


Where Your Loyalties Lie

by SoloShikigami



Category: Undertale (Video Game)
Genre: M/M, Mildly Dubious Consent, Posessive Papyrus (Undertale), Power Imbalance, Power Play, Sibling Incest
Language: English
Status: Completed
Published: 2020-05-12
Updated: 2020-05-12
Packaged: 2021-03-03 02:36:00
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,762
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24137482
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: After neutral run that leaves the Underground without their Royal Family and Royal Guard, Papyrus decides to go for becoming the leader of The Underground. Sans agrees to support him, but as his magic grows, so does his possessiveness over his brother.Sans isn't sure if he truly minds...
Relationships: Papyrus/Sans (Undertale)
Comments: 2
Kudos: 74





	Where Your Loyalties Lie

**Author's Note:**

> Based on art made by Gorryb and Ganz (https://soloshikigami.tumblr.com/post/180536638248/nsfwsinningsans-gorryb-nothing-wrong-here)

It had been a few months since the human child took a somewhat murderous rampage through the Underground. With the Royal Family gone along with the head of the Royal Guard, the Underground was a little lost with who should be the next ruler.

“Sans,” Papyrus said one evening over a broadcast of Mettaton as he covered the story of the passing of the Royal Family.

“‘Sup, Paps?” Sans asked, stretching his back as he lounged on the couch.

“Could you please sit up, this is important!” Papyrus said with an exasperated sigh.

Sans blinked, looking at Papyrus as he stood at the foot of the stairs. There was a very serious look on his face that made Sans slowly sit up, grabbing the television controller and putting it on mute.

“What’s on your mind?” Sans asked.

“I think I should rule the Underground,” Papyrus said evenly.

Sans stared at him for a moment as he ran the entirety of their life in Snowdin through his mind. The puzzles, the posturing, all of it in the name of becoming a Royal Guard, and therefore famous, and therefore popular, and therefore surrounded by friends and admirers.

His little brother wanted to be the King of Monsters?

Well, he supported him this far, but then again...

“Okay, Papyrus,” Sans said, crossing his arms and relaxing against the back of the couch. “Why do you think you should be the King of all Monsters? This isn’t like the Royal Guard, and there isn’t really anyone to train you like, well, you know...”

“Undyne. There is no one to train me like how Undyne was training me,” Papyrus’ voice strained as he remembered his one and, honestly, his only friend. “Don’t hide the truth anymore, Sans, I am not a baby bones. My friend Undyne is dust, there is nothing that can change that.”

Sans frowned as he realized a dark cloud had come over his usually bright and happy brother.

His soul ached at the sight.

“You’re right,” Sans said. “Well, you’re the coolest bone I know, Pap, and as long as you’re sure you want the responsibility, then you know I’ll have your backbone.”

Sans gave him a wink, and while a slight hint of annoyance flashed across Papyrus’ eyes, he smirked.

“So, you shall support me on my campaign?” Papyrus asked, straightening more, if at all possible.

“You know I will.”

“Even if it means ceasing your lazy habits?”

“Yeah, sure, whatever you need, bro.”

Papyrus has been stepping closer with each of his questions, but with legs as long as his, it didn’t take more than a couple of strides before he was standing over Sans.

“Do you promise?” Papyrus asked.

At first, Sans was going to brush him off, but there was an intensity in his eyes that made Sans feel a little unsettled, and it also made him realize that he really couldn’t deny Papyrus anything.

“You know how I feel about promises,” Sans said, his voice deepening slightly, thick as his eye lights went dark, his depression beginning to show.

That little detail didn’t escape Papyrus and he let out a quiet sigh to himself; yes, he knew how Sans felt about promises, and knew he felt it more keenly now that his friend behind the door to The Ruins has been silent since the human’s rampage began. Papyrus stepped forward more, putting his hands on Sans’ shoulders gently.

“I know, Sans,” Papyrus murmured softly. “Promise me this, because I promise _you_ that I will make everything right, and I will take care of you.”

“Heh, yeah, sure bro.”

“Promise me, Sans?”

The hands on his shoulders tensed and tightened. Sans sighed, reaching up and patting Papyrus’ hands.

“I promise.”  
~~~~~

_And this is why I hate making promises,_ Sans thought, shaking, his left eye glowing.

“It is over, Sans, you can relax,” Papyrus said, sweeping towards him with a warm smile.

“B-b-but, Papyrus, w-why?” Sans whispered, clutching his papers tight, unable to look around again at the bones sticking up from the floor.

“They were a threat to us, and to you, Sans; I did it to keep you safe,” Papyrus explained calmly, still smiling.

“But, but, why, you didn’t-?” Sans continued to stammer while also beginning to step back.

“Are you forgetting your oath, Sans?” Papyrus asked, the smile dropping slightly as he raised the hand not wielding the trident.

Sans stifled a gasp as he felt his brother’s blue magic surrounding his soul, weighing him down and keeping him from moving. Ever since stepping up as king, Papyrus’ magic power had increased to that of a Boss Monster. What scared Sans was that Papyrus was beginning to understand exactly how to use his new strengths and how to use them to his full advantage.

“Answer me, Sans,” Papyrus said, walking towards him. “Have you forgotten your oath?”

“O-of course not,” Sans murmured.

“Recite it for me, then, if you please?”

“My heart for the kingdom, my magic for the kingdom, my soul for the kingdom. I place myself at the mercy of my monarch, for they shall protect me, as I will for them,” Sans said, his voice even though his body was trembling.

“Excellent. I am glad that you have learned to be a loyal, productive servant under my rule, brother,” Papyrus said, his smile and general demeanor seeming to be back to the bright, friendly way Papyrus was known for. “I have given you quite a bit of leniency as my Royal Scientist; I have allowed you to wear your lab coat under that ridiculous hoodie of yours, I allow you to keep most of the hours you wish, though I may have to revoke your privileges of choosing your own staff, seeing as some of them seemed... traitorous.”

Papyrus glanced down at one particular bone with disdain, Sans knew that about ten minutes ago there used to be a monster standing there. He shook more as Papyrus towered over him, panicking briefly over what he was going to do, when he broke into the gentle smile that Sans has fallen in love with as he bent down to scoop up Sans with one arm, holding him close, one of Sans’ arms dropping limply to his side as he leaned against his brother.

“Do not worry, Sans,” Papyrus said as he nuzzled the top of Sans’ head. “The Great King Papyrus will make sure that you are safe and taken care of, no matter who attempts to protest.”

Sans wanted to shudder, but the blue magic was too strong and left him only able to sit where Papyrus held him very much like a rag doll, at the mercy of his owner’s whims.

~~~~~

As time went on, Papyrus only became more possessive, operating under the thought that he was doing what was right - his one priority was caring for his brother and protecting him. Sans soon found himself falling under his spell, giving in to what his brother wanted, even allowing him to keep custody over his soul.

Papyrus kept both Sans’ and his own soul next to his throne, both hearts caught up their own dance, which tended to keep Sans on edge all day. Not only could he feel Papyrus’ protective aura covering him like a shroud, he could also feel his love and lust for him, creating a war within between his mind and soul with his body and life hanging fairly literally in the balance.

“Papyrus, this has to stop,” Sans finally forced out one day after giving Papyrus his reports for the week.

“Are you having a problem with gathering the information you need for your reports? You know how difficult it is to find assistants who meet my very high standards,” Papyrus said. “I could give you a bit more time, if you need?”

“No!” Sans shouted, nearly doubling over, the papers slipping from his arms.

“Sans?! What is the matter?” Papyrus asked, sitting up.

“No, do-don’t get up, just, please, listen to me,” Sans said, Papyrus’ emotions affecting his soul. He glanced over to where the two hearts spun together by the throne. “Look, bro, please, I know you’re trying to protect me, but I need my soul back. I can’t work like this.”

“You have been doing admirable so far, I do not see any benefit to changing our arrangement,” Papyrus sighed. “Sans, come to me.”

Part of Sans wanted to resist, to fight this madness that was beginning to consume his brother and now him, but the pull was too strong. As much as he knew all of this was insane, he loved Papyrus, and he wanted to make him happy.

Papyrus sat forward on the throne, reaching out to wrap a hand around Sans’ waist to pull him close the moment he was in range. He sighed in satisfaction at feeling the smaller body in his arm, fitting just so, as if they were made for one another. Hell, in his mind, they were! Sans was a lazy monster and needed a cool skeleton like Papyrus to take care of him! He reached up with his other hand to trace the line of Sans’ jaw, reveling in the way Sans opened his mouth, loving and needing the touch as much as Papyrus wanted to give it.

“Ah, Sans, perhaps I have not been showing you my gratitude enough?” Papyrus asked.

“It’s not that,” Sans said, his voice weak and breathy, lifting his jaw slightly at the gentle touch.

“Maybe it is, perhaps if I showed you how much you mean to me, perhaps you wouldn’t be so resistant to my love and care,” Papyrus said, curving his hand under the mandible, his thumb pressing on top of the bottom set of teeth, keeping Sans’ mouth just slightly open. “I love you Sans, more than anyone else ever could or will, and I will prove it to you.”

Sans lifted his hands to keep Papyrus back, to protest and insist on being heard, but the arm around him lifted slightly and pulled him forward, which resulted in bending him back over Papyrus’ arm. Papyrus leaned forward, his tongue slipping into Sans’ mouth, pressing against the forming blue one, overtaking the smaller skeleton completely.

Sans trembled in his brother’s grasp, tears burning in his eye-sockets before making twin trails down either side of his face. This was his life, now, and there wasn’t any way that he was going to get out of it.

And what truly made it worse was that he no longer wanted to.

**Author's Note:**

> Like what you read? Please check out my social media for more fun!  
> [ My Tumblr](https://soloshikigami.tumblr.com/)  
> [ My Twitter](https://twitter.com/SoloShikigami)


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